Approach control system



Feb. 10, 1942. HQ G. BLossER 2,272,739 I APPROACH CONTROL SYSTEM F'il'ed Aug. 24, 1940 Patented Feb. 10, 1942 APPROACH CONTROL SYSTEM Bierman G. Blosser, Pittsburgh, Pa., assignor to The Union Switch & Signal Company, Swissvale, Pa., a corporation of Pennsylvania Application August 24, 1940, Serial N0. 354,097

3 Claims.

My invention relates to approach control apparatus for use in railway signaling systems of the coded track circuit class, and particularly to an improvement in the systems shown in my Letters Patent of the United States No. 2,174,255, issued September 26, 1939, and in Letters Patent of the United States No. 2,172,893, issued September 12, 1939, to Edward U. Thomas,

The systems shown in the above mentioned patents incorporate means at the entrance end of each track section and operative when the track section is vacant to supply impulses of feed back energy to the section rails during the oif periods in the master code which is supplied to the section rails at the exit end of the section. In addition, the systems shown in the above mentioned patents have at the exit end of each track section a code following detector relay which responds to the impulses of feed back energy and controls the supply of energy to a slow releasing approach relay.

The system shown in the patent to Thomas provides means for prolonging thepicked-up periods of the code following detector relay to thereby increase the period of time during which energy is supplied to the approach relay and correspondingly decrease the release time of the approach relay.

In the system shown in the Thomas patent the increase in the picked-up periods of the detector relay is obtained by providing this relay with a holding winding which is supplied with energy over a lcircuit which includes a front contact of the relay as well as a contact of the coding relay or other device for supplying master code energy to the section rails. This arrangement operates so that the holdingfwinding of the detector relay is energized as soon as the relay contacts pick up and is maintained energized until the end of the off period in the master code.

In the system shown in the Thomas patent the detector relay is provided with another or second contact which when picked up establishes a circuit to supply energy to the winding of the slow releasing approach relay. Since the system shown in the Thomas patent requires the detector relay to be provided with two or more contacts, it is impossible to employ as sensitive a relay for this purpose as could be employed if this relay were required to have only one contact.

It is an object of my invention to provide an improved signaling system of the type described having a circuit controlled by a single contact of the detector relay for energizing both the holding winding of the detector relay and the winding of the approach relay.

A further object of my invention is to provide an improved system of the type described l and in which the circuits of the holding winding of the detector relay and of the winding of the approach relay are arranged so that neither relay will adversely aifect the operating characteristics of the other relay.

Another object of my invention is to provide an improved signaling system.

I shall ydescribe one form of signaling system embodying my invention, and shall then point out the novel features thereof in claims.

In the drawing the single figure is a diagram of a section of railway track equipped with the improved approach control apparatus provided by my invention. l

Referring to the drawing, there is shown therein a stretch of railway track having track rails I and 2 over which trac normally moves in the direction indicated by the arrow, that is from left to right. The rails of the track stretch are divided by insulated joints 3 into the customary successive track sections. One such section is shown and is designated section I 2T.

The track section |2T has at the entrance end thereof a code following track relay IZTR which receives energy over the section rails. The track relay has associated therewith suitable decoding means shown diagrammatically in the drawing for controlling the signal 2S and also controlling the supply of coded energy to the adjacent track section in the rear in accordance with the irequency of the coded energy supplied to the track relay. The construction and operation of this decoding means is not a part of this invention and any means well-known in the art may be employed for this purpose.

The track section has at the eXit end thereof means for continuously supplying to the section rails direct current master code energy of one or another of a plurality of different code frequencies. In a typical three-indication system such as that shown in the drawing, energy coded at two different rates is employed and these two rates may -consist of '75 and 180 energy impulses per minute which are separated by intervals of substantially equal duration during which no energy is supplied. Selection between the two rates of energy supplied to the rails of a track section is made in accordance with advance traiic conditions in the customary manner.

The equipment at the exit end of the track purpose.

The equipment is shown in the drawing in the condition which it assumes when the track stretch is vacant. At this-time energy of 180 code frequency is supplied to the coding relay CR by means not shown, and the contacts 2D and 2l of this relay. are picked up and released at this rate. These contacts when released establish connection to supply an impulse of master code energy from the track battery I2TB to the rails of section |2T and this energy feeds to the track relay IZTR and picks it up.

After a brief time interval, the contacts of the coding relay CR become picked up and terminate the impulse of master code energy supplied to the section rails and establish the circuit to permit feed back energy to be supplied over the section rails to the pick-up winding 24 of the relay IZKR.

On termination of the impulse of master code energy the track relay IZTR releases and an impulse of energy is supplied through the transformer I2TT to pick up the impulse relay IZIR to thereby disconnect the track relay I2TR from the section rails and to supply an impulse of feed back energy from the battery I 2AB to the section rails. The impulse of feed back energy feeds from the section rails to the pickup winding 24 of the detector relay I ZKR over the circuit which is traced from track rail I, through front contact 20 of coding relay CR. and winding 24 to track rail 2.

As a result of the supply o f energy to the pickup winding 24 of relay IZKR, the contact 25 of this relay picks up and establishes a4 circuit for supplying energy from the battery IZTB to the winding of the approach relay I2AR and to the holding winding 26 of relay IZKR in series. This circuit is traced from one terminal of the battery IZTB through front contact 2l of coding relay CR. winding of relay IZAR, winding 26 of relay IZKR, and front contact 25 of relay |2KR to the other terminal of the battery.

The energy supplied to the holding winding 2E of the relay IZKR maintains the relay contact 25 picked up as long as the circuit of the winding 26 is maintained. The circuit of this winding is interrupted on release of the contacts of the relay CR to initiate the supply of an impulse of master code energy to the section rails. When contact 2| of relay CR releases, it interrupts the circuit of the winding of the relay IZAR and of the holding winding 26 of the relay I2KR so that contact 25 becomes released and additionally interrupts the circuit of these windings.

During the neXt and subsequent picked-up periods of the contacts of the coding relay CR, impulses of feed back energy are supplied to the pick-up winding 24 of the detector relay I2KR and contact 25 picks up and completes the circuit for supplying energy to the holding winding 26 of the detector relay IZKR and to the winding of the approach relay |2AR. Similarly, during subsequent released periods of the contacts of the coding relay CR, the circuit of the winding of the approach relay and of the holding winding 26 of relay IZKR is interrupted.

The relay IZAR has a snubbing resistor connected across the terminals of its winding to render its contact slow to release with the result that the contact remains picked up during the intervals between the supply of impulses of energy to the relay winding.

Accordingly, as long as the track section is l vacant, the detector relay I2KR responds to the impulses of feed back energy supplied over the section rails and contact 25 establishes the circuit for supplying impulses of energy to the winding of the approach relay IZAR so that the contact 28 of this relay is picked up and interrupts the circuits of the lamps of the signal ISS.

When a train enters the track section, the supply of feed back energy over the section rails is cut oi and the detector relay thereafter remains released and energy is no longer supplied to the approach relay I2AR with the result that its contact 28 releases and establishes the circuit to supply energy to the lamps of signal |35.

When the track section is vacated, the detector relay again responds to feed back energy so that energy is again supplied to the winding of the approach relay I2AR and its contact 28 is picked up and interrupts the circuits of the lamps of signal 13S.

It will be seen that the circuit provided by this invention is arranged so that only a single contact is required on the detector relay KR to properly control the circuit of both the holding winding 26 of the detector relay and the winding of the approach relay. As the detector relay is only required to have one contact, this relay may be of a type which is extremely sensitive so that the relay will respond to the impulses of feed back energy even though these impulses are of Very small value.

In addition, it will be seen that although the circuits of the winding of the approach relay and of the holding winding of the detector relay are both controlled by the same Contact of the detector relay, the circuit is arranged so that these relays do not alter the operating characteristics of each other.

In the system provided by this invention when the contact of the relay |2KR is released, the circuit for supplying energy to the winding of the approach relay and to the holding winding of the detector relay is interrupted. Furthermore, at this time connection from one terminal of the holding winding of the detector relay and the winding of the approach relay is interrupted. Accordingly, on the supply of an impulse of energy to the pick-up Winding of the detector relay and resultant building up of flux in the core of the relay there is no possibility that the pick-up and holding windings of the detector relay will operate as the primary and secondary windings of a transformer to supply energy to the winding of the approach relay as would occur if both terminals of the detector relay holding winding and the approach relay winding were connected together. If this transformer action did occur, the building up of flux in the core of the detector relay would be delayed and suflicient flux might not be developed in this core to pick up the relay contact before the end of the impulse of energy is reached. Since the circuit provided by this invention is arranged so that this transformer action cannot occur, the full value of the impulses of feed back energy is available to pick up the relay contacts and this relay is certain to respond to these impulses.

Although I have herein shown and described only one form of approach control apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the scope lof the appended claims Without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In-a coded railway signaling system, in combination, a section of railway track over which traic normally moves in a given direction, a coding device at the exit end of the section for supplying to the section rails master code signal control energy consisting of alternate on and off periods, means at the entrance end of the section and elective when said section is vacant for further supplying to said section rails impulses of feed back energy during the off periods in the master code, a code following detector relay and a slow release approach relay at the exit end of said section, said detector relay having a pickup and a holding winding, and means controlled by said coding device and operative during the 01T periods in the master code to connect the pick-up winding of said detector relay in energy receiving relation with the rails of said section and to establish a circuit over which energy may be supplied to the holding winding of said detector relay and to the winding of the approach relay in series, said circuit being interrupted as long as said detector relay contact is released and being completed on picking up of said Contact.

2. In a coded railway signaling system, in combination, a section of railway track over which traiiic normally moves in a given direction, a source of current and a coding device at the exit end of the section, said coding device having a plurality of contacts movable between a rst and a second position, said contacts being operative in their rst position to establish connection from said source of current tothe section rails and being operative in their second position to interrupt such connection, whereby as a result of movement of the coding device contacts between their two positions master vcode signal control energy consisting of alternate on and oi periods is supplied to the section rails, means at the entrance end of the section and eiective when said section is vacant for further supplying to said section rails impulses of feed back energy during the 01T periods in the master code, a code following detector relay and a slow release approach relay at the 'exit end of said section, said detector relay having a pick-up and a holding Winding, means controlled by one contact of said coding device and operative when said contact is in its second position to connect the pickup winding of said detector relay in energy receiving relation with the rails of said section, and a circuit including a second contact of said coding device and said contact of said detector relay for supplying energy to the holding winding of said detector relay and to the winding of the approach relay in series, said circuit being complete when said coding device contact is in its second position and said detector relay contact is picked up.

3. In a coded .railway signaling system, in cornbination, a section of railway track over which traffic normally moves in a given direction, a coding device at the exit end of the section for supplying to the section rails master code signal control energy consisting of alternate on and 01T periods, means at the entrance end of the section and eiective when said section is vacant for further supplying to said section rails impulses of feed back energy, a code following detector relay and a slow release approach relay at the exit end of said section, said detector relay having a pick-up winding to which is supplied from the section rails impulses of feed back energyl said detector relay also having a holding winding and being provided with a contact which is normally released and which becomes picked up when an impulse of feed back energy is supplied to the relay pick-up Winding, and means y controlled by said coding device for establishing a circuit over which energy may be supplied to the detector relay holding winding and to the approach relay winding in series, said circuit being interrupted as long as the detector relay contact is released and being completed when said contact picks up.

HERMAN G. BLOSSER. 

